A game of “pin the motive on the suspect”? It’d be like pin the tail on the donkey only with motives (wants the inheritance money, vengeance for an affair, jealousy of victim’s success, etc.) on pieces of paper that you have to pin to the suspect’s brain.
Take a picture of each of your party members at the start of the party and then put them on to see what people deduce about each of you for fun.
A treasure hunt where the group has to figure out a series of codes or clues that relate to Sherlock and eventually lead to a prize at the end for each player, like a treasure chest of gold chocolate coins (like the Agra treasure, or because in BBC Sherlock, he wanted to be a pirate.)
Making black lotuses out of origami paper a la The Blind Banker.
Making chalk outlines of all the party members on your driveway to make it look like a murder scene.
Setting up a fictional murder scene in your house so your guests have to make secret guesses on how it happened. You can find some of these online. 🙂 Have them write down their guesses in a note and put it in “Lestrade’s Inbox”. Give them some sort of Scotland Yard award for the person who is closest to the real happenings.
A dramatic out-loud reading of a short PG 13 (or worse if you were my friend) fan-fiction.
Setting up a minibar with beakers full of colorful non-alcoholic drinks and mixers so people can perform their own “chemistry experiments”.
If I think of any more later on, I’ll come back and edit.